1. Technical Field
The invention relates to semi-trailers, and in particular to the steerable lift axle/suspension systems of the trailer of a semi-trailer. More particularly, the invention relates to the mounting of steering dampers and a backup lock on the suspension assembly beams rather than on the axle.
2. Background Art
Prior art steerable lift axle/suspension systems of semi-trailers or tractor-trailers typically have the steering dampers and the backup lock of the system mounted directly on the axle and, specifically, on the central axle tube portion of the axle which generally is located inboard from each of the suspension assembly beams. Manufacturers of steerable lift axles typically supply and assemble special brackets for mounting these components directly on their axle, then mount suspension assemblies on the axle or, alternatively, sell the axle to trailer builders who then mount the suspension assemblies on the axle. This practice either causes the steerable axle manufacturer or the trailer builder to become heavily involved in suspension assembly geometry layout work. Many problems and/or limitations often result from this manufacturing arrangement because axle manufacturers and trailer builders typically have less then complete familiarity with the complexities of suspension assembly design.
The present invention solves the noted problems by mounting the steering dampers and the backup lock on the suspension assembly beams via support brackets rather than on the axle tube. By locating these components on the suspension beams rather than on the axle, stresses to the axle caused by mounting components or brackets thereon also are eliminated. Eliminating such stresses, in turn, eliminates the possibility of axle tube failures caused by those stresses. To compensate for such stresses, axle manufacturers heretofore have made the walls of steerable suspension axle tubes thicker, with the undesirable result of adding weight to the vehicle.
The present invention also enables the suspension manufacturer to be more completely involved in the design of the overall axle/suspension system, Which results in improved performance characteristics, more compact design, ease of installation, and reduced weight. It also benefits the end user because the user can turn to one supplier, that is, the suspension manufacturer, rather than many suppliers, including axle and trailer manufacturers, to service the system.
In addition, the location of the component mounting brackets on the inboard side of the, suspension beams by bolt attachment is advantageous because, if a problem occurs with the components or brackets, new parts can be obtained and the defective parts easily replaced or repaired. In the past, problems with the brackets or the mounted components also could cause damage to the axle tube, resulting in the need to replace the entire axle. Such repairs are expensive and time-consuming because they involve much cutting, welding, and fixturing.